function tt_gallery_shortcode($attr)
{
global $post;

static $instance = 0;
$instance++;

// Allow plugins/themes to override the default gallery template.
$output = apply_filters('post_gallery', '', $attr);
if ( $output != '' )
return $output;

// We're trusting author input, so let's at least make sure it looks like a valid orderby statement
if ( isset( $attr['orderby'] ) ) {
$attr['orderby'] = sanitize_sql_orderby( $attr['orderby'] );
if ( !$attr['orderby'] )
unset( $attr['orderby'] );
}

extract(shortcode_atts(array(
'order'      => 'ASC',
'orderby'    => 'menu_order ID',
'id'         => $post->ID,
'itemtag'    => 'li',
'icontag'    => 'span',
'captiontag' => 'div',
'columns'    => 0,
'size'       => 'thumbnail'
), $attr));

$id = intval($id);
$attachments = get_children( array('post_parent' => $id, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby) );

if ( empty($attachments) )
return '';

if ( is_feed() ) {
$output = "\n";
foreach ( $attachments as $att_id => $attachment )
$output .= wp_get_attachment_link($att_id, $size, true) . "\n";
return $output;
}

$itemtag = tag_escape($itemtag);
$captiontag = tag_escape($captiontag);
$columns = intval($columns);
$itemwidth = $columns > 0 ? floor(100/$columns) : 100;

$selector = "gallery-{$instance}";

$output = apply_filters('gallery_style', "
<ul class='thumbs noscript'>
");

$i = 0;
foreach ( $attachments as $id => $attachment ) {

$link = isset($attr['link']) && 'file' == $attr['link'] ? wp_get_attachment_link($id, $size, false, false) : wp_get_attachment_link($id, $size, false, false);
$link = str_replace('<a href=', "<a class='thumb' href=", $link);

$link_title = "<{$captiontag} class='caption'> <div class='image-title'>" . wptexturize($attachment->post_title) . "</div>";

$link_caption = "<div class='image-excerpt'>" . wptexturize($attachment->post_excerpt) . "</div>";

$link_description = "<div class='image-description'>" . wptexturize($attachment->post_content) . "</div> </{$captiontag}>";

$output .= "<{$itemtag}>
";
$output .= "$link
";
$output .= "$link_title
";
$output .= "$link_caption
";
$output .= "$link_description
";
$output .= "</{$itemtag}>
";

if ( $columns > 0 && ++$i % $columns == 0 )
$output .= '';
}

$output .= "
</ul>\n";

return $output;
}

add_shortcode('gallery', 'tt_gallery_shortcode');